This invention relates to improved surfactant-based 1,1-dichloro-1-fluoroethane drying compositions. More particularly, this invention relates to such compositions which include a volatile solvent component such as 1,1-dichloro-1-fluoroethane and one or more compounds that have the capability of removing water or aqueous films from the surfaces of a broad range of substrates.
Various volatile solvent drying compositions have been used in the past. Illustrative of such compositions are those described in U.S. Pat. Nos. 4,438,026 and 4,401,584 and German Patent No. 3,319,023. These compositions remove water from the substrate to be dried by displacement. Drying in this manner avoids an energy consuming drying step and greatly expedites subsequent processing of the substrate component.
Prior art drying compositions suffer from a number of disadvantages which limit their usefulness. For example, some volatile solvent drying compositions used in the past have often proved less than satisfactory by failing to effectively displace water from the surface to be dried. Also, although some compositions in the past have proven effective to displace water from some substrates such as metal, e.g. stainless steel, aluminum and brass, they have not been practically effective on nonmetallic surfaces, such as glass or ceramic.
An additional and serious problem encountered with varying severity in the use of solvent drying solutions depending on the specific application and substrate to be dried, is the fact that such solutions tend to emulsify or otherwise generate agglomerates and are difficult to purify or to be freed of aqueous impurities so that the drying solution can reused. The presence of emulsions or other non-soluble formations in these drying compositions interferes with the free elimination of water, such as by decantation, and ultimately interrupts the water-displacement process which is the essential objective of the substrate drying treatment.
In some dewatering compositions, the tendency to form emulsions with water is controlled by the incorporation of suitable demulsifiers. While such additives do prevent emulsification, they do not improve the effectiveness of the compositions for dewatering all substrates. Moreover, some of these surfactants have excessive water extract ability which necessitates the addition of more surfactant to the composition on a periodic basis.
The art is continually seeking new fluorocarbon based drying compositions. Currently, fluorocarbon based compositions which are considered to be stratospherically safe substitutes for presently used fully halogenated chlorofluorocarbons are of interest. The latter are suspected of causing environmental problems in connection with the earth's protective ozone layer. Mathematical models have substantiated that hydrochlorofluorocarbons, such as 1,1-dichloro-1-fluoroethane (HCFC-141b), will not adversely affect atmospheric chemistry, being negligible contributors to ozone depletion and to green-house warming in comparison to the fully halogenated species.